Two tickets to A Minister's Wife. A new musical adapted from George Bernard Shaw's Candida by Austin Pendelton, with music by Joshua Schmidt and lyrics by Jan Tranen.    A MINISTER'S WIFE explores the fires burning beneath the surface of a seemingly ordinary marriage: The Reverend James Morrell and his wife, Candida, are happily married - or at least they think - until a romantic young poet enters their life, turning their world upside-down.  Previews start April 7, 2011; Opening Night May 5, 2011.  Lincoln Center Theater.